WO2014023282A1

WO2014023282A1 - Blown film installation, method for producing a blown film strip and film produced therewith

Info

Publication number: WO2014023282A1
Application number: PCT/DE2013/000441
Authority: WO
Inventors: Edgar Gandelheidt
Original assignee: Reifenhäuser GmbH & Co. KG Maschinenfabrik
Priority date: 2012-08-07
Filing date: 2013-08-07
Publication date: 2014-02-13
Also published as: DE202013012821U1; EP2849929A1; CN104540660B; EP2952330B1; DE112013003972A5; EP2849929B1; EP3508327A1; CA3132282C; BR122017008963A2; EP3266590A1; ES2612713T3; ES2839498T3; CA3132282A1; CN104540660A; DE202013012822U1; US10137629B2; CA2872835A1; BR112014031115B1; CN107825682A; US10906232B2

Abstract

In blown film installations, it is known to provide longitudinal stretching of the produced double layer film strip downstream of the draw-off, more precisely downstream of the reversing unit and upstream of the winder. It is also known to stretch the down-drawn film, wherein the film must then be preheated owing to the long cooling path from the draw-off. According to a first feature, the present invention specifies warming the film above the draw-off and then treating it mechanically. The film can thereby be brought with only little energy from a first level of warmth to a temperature level at which it can easily be worked. According to a second feature, the invention specifies providing a tractive force breakdown brake.

Description

Blown film plant, process for producing a blown film web and thus produced

foil

[01] The invention relates to a blown film plant, to a process for producing a blown film web and to a film produced therewith. [02] Blown film plants are known. The plants are supplied with plastics in granulated form, which are then plasticized in extruders under high pressure to a viscous mass. This mass is annular in a die and escapes the die through an annular die. When leaving the ring nozzle, the mass already forms a film tube. The film tube is pulled up along a tube forming zone, in which compressed air is introduced into the interior of the film tube. This leads to a transverse stretching of the film tube. By means of an active coolant for the ascending film tube, a cooling of the melt is achieved within a tolerable distance from the annular nozzle. The film tube runs on its way up in mostly semi-crystalline state a calibration and then a flattening, which flattened the tube. The flattening unit feeds the double-layer film web to a preliminary squeeze. The pre-squeezing usually consists of a pair of rollers, through the nip - often called "nip" - the film passes through the pre-squeezing follows a squeezing, in which the film tube finally a virtually air-free double-layer film web is formed The distance from the pre-squeeze to the squeeze is such that during the transport between the two pairs of rolls the film can emit heat originating from the extrusion process, in this way the film tube is additionally cooled, so that it can then be further processed, for example, a split of the film tube, resulting in two separate film webs. [03] Many plants work without pre-squeezing, but instead feed the foil directly from the flattening to the squeeze. Even with such a system construction, the rising foil is already so strongly cooled in the pair of nip rollers that a powerful attack on the surface of the foil does little or no damage. Because the squeezing pulls the film in the normal case at a much higher speed up than is extruded at the ring die. An exemplary speed ratio is 10: 1 to 20: 1. The blown film is immediately pressurized with compressed air from the inside when forming the tubular form above the annular nozzle and thereby drawn in the transverse direction. At the same time, the squeeze roller pair pulls the film upwards at high speed, so that it comes to a longitudinal stretching below the frost line.

Overall, therefore, the film tube is biaxially stretched below the frost line. Depending on the intended application of the film end product, the longitudinal or transverse joint portion may predominate.

[05] However, a blown film system always has to contend with the technical disadvantage that the optical film quality can not keep up with the film quality of cast films. This is because the rising film tube shape cools relatively slowly. The longer the cooling process of the plastic melt lasts, the cloudier and glossier the film surface becomes.

[06] However, in order to be able to exert sufficient force on the ascending foil with the squeegee pair, the film must be relatively cooled. In view of the slow cooling rate of the extruded film, this leads to a high installation height in blown film lines. Above the squeeze, the double-layer film web is therefore deflected as quickly as possible into the horizontal, guided next to the system and from there downwards for the further treatment steps. Usually, next to the installation at the bottom of the installation site, there is a winder which winds the double-layered film web onto a roll for further transport. Stretching devices are sometimes provided in front of the winder, in the context of the present patent application the term "stretching / stretching" being understood as a generic term for "stretching" and "stretching".

[08] A "stretch" system will stretch the film over 5%, at least in the longitudinal direction, preferably 50% and more, often up to 1,000%. Such systems are often referred to as "MDO", which means "machine direction orientation ", ie for orientation of the plastic molecules in the machine direction, ie the direction of transport of the material through the system.

[09] A stretching machine is disclosed, for example, in DT 2 146 266. There, extruders reverse on a scaffold above a vertical blowing line. To the pair of take-off rollers, a set of rollers joins until a second pair of nip rollers is reached. The second nip roll runs faster than the first, so that the double-ply film web is given the stretch in the machine direction. The cooling path of the film tube before the first pair of squeezing rollers can be set so that it passes through it at the maximum possible temperature so that stretching can ideally take place without temperature supply. Also, the stretch ratio can be adjusted, simply by the second pair of nip rolls, since the rolls to be attributed to the rolls are passive or at least passive at the beginning.

[10] As an alternative to a MDO, a so-called flatness package may be provided as a stretching device in front of the winder. This irreversibly "straightens" the film between 0.5% and 5% in the machine direction, which only serves to compensate run length differences across the width of the double-layer film web and in the direction of straight travel of the film web, so that the film can be better wound up and processed further.

[1 1] Both stretching devices, ie an MDO and a flatness package, are technically well comparable insofar as they make a longitudinal stretching of the film. For this purpose, after a first, slower roller immediately following or, for example, after further, passive rollers a faster driven roller. Due to the difference in speed of the two rollers, which can also be designed as nip roller pairs, which each transport the film with static friction, there is a change in length of the film.

[12] The distance between the two areas in which the film is transported at the circumferential speed of the respective roller is referred to as "stretched section", or in the machine direction projection as "stretched length".

[13] In an approximately central section of the wrapping of the film web around a roller, the film web is transported with static friction, thus with the peripheral speed of the roller. Even before the film web leaves the roll surface at a lifting point, the stiction ends. This is especially important when the subsequent roller runs at a higher peripheral speed, so the film web so already on the roll surface of static friction initially passes to faster sliding friction and only then lifts off the roll surface.

[14] The same principle can also be observed when running on a roller: the film web already has contact with the peripheral surface of the roller from a point of contact, but the static friction only begins beyond the contact point.

[15] Simplicity is referred to herein as "dots." A film web lifts off a roller at a release line and rides on a roller surface with a lay-up line, but when viewed from the side, the two-dimensional film web is reduced by one dimension to one line Accordingly, the lift-off and lay-up lines are each reduced by one dimension to points.

It should be noted that for the film transport instead of a roller usually a nip roller pair can be used as well. The present application speaks for the sake of simplicity usually only of a roller, but it means as well as a squeeze roller pair as a professional replacement agent. [17] A squeeze roller pair can tend to cause a safer gripping of the film because the film surfaces are gripped from both sides. However, even from one side attacking roller can exert a sufficient longitudinal force on the film, which For example, depends on the surface design of the roller in interaction with the respective film to be processed and, for example, the wrap angle of the roller. In any case, in the case of a simple driven roller, it is customary to provide a pressure roller in order to ensure more reliably that the foil can actually be gripped by the driven roller to the exclusion of slipping.

The invention has for its object to improve the prior art or to provide him with an alternative.

According to a first aspect of the invention, this object is achieved by a blown film plant comprising a ring die for extruding a film tube, having a tube forming zone for longitudinally and transversely pulling the foil tube, with a coolant for the film tube moving in the machine direction, with a flattening for the Film tube to a double-layer film web and with a pair of take-off rollers beyond the coolant for withdrawing the film tube, being provided in the machine direction beyond the pair of withdrawal rollers, a treatment roller path for longitudinal stretching of the double-layer film web with a heating means for the Doppellagenfolienbahn, wherein the blown film plant characterized in that the machine direction vertically from below is oriented upward and the treatment roller track is arranged above the pair of take-off rollers.

[20] The following is explained conceptually: [21] The "take-off roller pair" may, as explained above, preferably be a simple take-off roller pair, but it is also within the scope of the present invention if the pair of take-off rollers is preceded by a preliminary take-off roller pair Deduction is often referred to as squeezing or squeezing.

[22] In the case of such an arrangement with two pairs of rollers, the final squeezing-off roller pair is usually above the pair of preliminary rollers.

[23] Compared to the existing rolls or roller pairs, a pair of delivery rollers differs in principle in that it either completely the hose flattened or almost completely flattened leads, so as a double-layer film web. The take-off roller pair engages on both sides of the flattened film on its surface, also to thereby reduce the possibility upwardly depressed compressed air from the interior of the film tube. Often the diameter of a take-off roll is about 300 mm, often have diameters between 200 mm and 400 mm or more. If additionally Vorabzugswalzen are provided, these are often the same size as the take-off rolls.

[25] The "treatment roller path" is a designated transport path for the double-skin film web within which the double-layer film web is to be subjected to mechanical and thermal treatment, with an irreversible stretching being considered in the machine direction, ie at the local level Foil longitudinal direction of the transport.

[26] At least two, three, four, five, six or more rollers (or squeeze roller pairs) are provided for the treatment roller track, and these should fulfill at least two, three, four, five, six or more different functions within the treatment roller track. In particular, the functions should include: holding, heating, stretching, annealing, cooling, spreading, embossing or laminating.

[27] A roller can perform several functions simultaneously, such as holding and heating.

[28] Normally, the smallest possible number of rollers is desired.

The "heating means" should be an active heating means, so in particular provided with a current flowable heating coil, an infrared radiator, a laser emitter, a Heißwasserdurchströmungsleitung, an oil heater, generally a fuel-driven heating with a circuit and / or a comparable active heating means Extrusion heats up a lot of heat, which goes up anyway, and the fact that the film tube carries heat and carries it into the suit causes In addition, the system components above the pair of take-off rollers are quite warm when the system is running. However, these passively heating components are not meant by the heating means. Rather, an active heating means should actually be provided.

[30] In most cases, such a heating means will be recognizable by the fact that it has a temperature sensor in addition to the actual heater, or that the heating means has a control, in particular with a hysteresis control.

[31] In this context, it should be noted that in the context of the present patent application, whenever a "rule" is spoken, as a subset also a "control" should be included in content. By the term "control" is meant in particular a technical "control" meant, ie with a sensor for balancing the current values, but also includes a "control" is, for example, a heating coil, which is turned on only at intervals and then turned off again ,

[32] Alternatively or cumulatively to a temperature sensor on the heating means, a heating means can also be easily distinguished from an apparatus that has become hot during operation because the heating means can quickly be used to heat up the relevant heating medium even in a cold installation. The heating means is thus used for heating, which is faster than the heating of the system components in the upper part of the system would go into operation of the plant vonstatten.

With a positioning "above" the pair of withdrawal rollers is in a particularly preferred embodiment meant such a design in which the treatment roller track is at least partially vertically directly above the pair of withdrawal rollers, in a projection on a horizontal plane, which runs through the deduction roller pair, So would lead to an overlap with the projection of the take-off roller pair.

[34] It may be sufficient if a surrounding line around the treatment roller track can be projected in this way. So it is not necessary for that one of the rollers of the treatment roller track can be projected with an overlap on the horizontal, the latter being a preferred embodiment.

[35] It is considered to be particularly advantageous if at least one, two, three, four, five, six or more rolls of the treatment roller track lie parallel to the axis in the space to the take-off rolls.

[36] Each roller can - as already mentioned - be replaced by a pair of nip rollers

[37] Alternatively and cumulatively, the rolls of the treatment roller track can be of the same order of magnitude as the take-off roller pair, for example with diameters between 200 mm and 400 mm or more, preferably between 250 mm and 300 mm, and also clearly smaller than the take-off roller pair. for example, with diameters between 100 mm and 200 mm or less.

[38] A particularly compact arrangement results when at least one roller of the treatment roller track, preferably two, three, four, five, six or more rollers of the treatment roller track, each projecting at least half overlapping onto one or both of the take-off rollers in the horizontal lets or let. In such an embodiment, the rollers of the treatment roller track are quite compact above the deduction rollers.

[39] Alternatively and cumulatively, it is advantageous if rollers of the treatment roller track also overlap one another at least halfway when projecting onto the horizontal.

[40] It is understood that a greater overlap than half can be even more advantageous with proper design.

[41] Not quite so compact, but still within the extended scope of the invention, would be a somewhat different geometric relationship in which the aforementioned projections do not directly lead to overlap with the take-off roll. Rather, a circular surrounding around the pair of withdrawal rollers is intended. The surrounding area forms a horizontally lying, circular area. If the vertical projection of one, several or even all rollers of the treatment roller track falls into this area, in part or even completely, a very compact system shape is still achieved. In simple words, then the rollers of the treatment roller track are not necessarily exactly vertically above the pair of take-off rollers, but in the immediate vicinity.

[42] In a broader sense, the "above" may also be realized if the treatment roller section is provided laterally next to the pair of delivery rollers or the upper area of the blown film line, but at least with a roller of the treatment roller path geodetically higher than the pair of take-off rollers is preferably with several or even all rollers of the treatment roller track, in the case of a roller pair the geodetic height of the roller pair nip is considered in this connection.

[43] It is particularly advantageous for the arrangement of the treatment roller track above the pair of take-off rollers with a heating means for the double-layer film web to be used to heat the film over a temperature which the film has after passing through the take-off rollers. It has already been explained that the film must have undergone cooling to safely pass through the deduction roller pair, because there forces are exerted on the film. It must therefore be cooled below a temperature at which dimensional stability is present in order not to damage the film.

For a mechanical further processing of the film, in particular in the form of stretching by means of tensile force, it may be advantageous if the film is heated. For example, an MDO heats the film before the mechanical longitudinal stretching via a powerful heating roller.

[45] The invention has recognized that the film can benefit from the heat rising from the extruders and the blow head on the way up instead of down. Although it is not quite as easy to cool the film when climbing, but can within the treatment roller track be assumed that lower temperature gradients occur. Compared to the DT 2 146 266 can therefore be produced with surprisingly much better quality.

[46] Because the invention starts where the first heat is still present, ie the film has just cooled enough for gripping by the pair of draw-off rollers - the other way around is still relatively warm, therefore does not need to be warmed up so much. It proposes to provide the heating means above the take-off roller pair, because there the heating medium does not need to reheat as much as would be necessary with other positions in the system. For any kind of mechanical processing, which requires heat, this arrangement also leads to a significant energy saving.

In the prior art, such an arrangement is nowhere to be found: EP 1 147 877 A2 discloses in its second embodiment in Figure 5 a production line for stretch film, but in the stretched section between the Dehnwalzenpaaren the first heat is no longer present, because There, the double-layer film web is guided around the pair of withdrawal rollers around to the side and only later stretched. In particular, there is little or no rising first heat from the blown film process.

[48] The same applies to US Pat. No. 6,413,346 B.

[49] US 2,976,567 shows a Giesfolienanlage, no blown film plant. Therefore, there is no pair of take-off rollers, moreover, the effect of the large heat accumulation above the Blaskopfes and thus above a pair of nip rollers just not available.

In US Pat. No. 7,396,498 B, an optional stretching of the double-layer film web takes place at the very bottom right next to the blow head, so to speak, on the hall floor.

[5] US 5,458,841 performs a longitudinal stretching between a Vorabzugswalzenpaar and the take-off roller pair, above the rising blown film. However, there is currently no heating provided for the film, but rather the reference designates the stretched section as a "cold orientation zone." In addition, no mechanical treatment takes place above the final take-off roll pair. sen is there via a guide roller immediately in the horizontal and finally continued down.

[52] In DT 1 504 461, an internal mandrel for heating the film tube is provided. The first pair of take-off rollers does not close. The stretching after the first take-off roller pair takes place through overflowing overpressure.

[53] In AT 267 160, the blown film is embossed within the pair of draw-off rollers.

[54] The AT 342 292 provides that the tubular film is passed through a series of infrared heaters, which raise the temperature of the tubular film to the temperature required for drawing. The tubular film is then stretched in the direction transverse to the extrusion direction by introducing compressed air into it through a tube and at the same time stretched in its longitudinal direction by means not shown, which effect airtight closure of the tube and pull it off at a rate greater than the speed at which it is transported by pinch rollers. The straight darve not shown means for the Längsverstreckung are therefore in the local sense the take-off rolls, and beyond which apparently no further treatment, quite apart from the fact that the document extruded from top to bottom and therefore the heat advantage of the rising heat can use worse anyway ,

[55] The CH 432 815 is also concerned with the construction of the plant in front of the pair of draw-off rollers, but not with the design beyond the pair of draw-off rollers.

[56] The same applies to CH 475 082.

[57] DE 21 32 259 C3 describes a rather remote prior art.

DE 102 42 174 A1 describes a conventional blown film line, wherein the longitudinal stretch factor or the blow-up factor should be set by means of the ratio between the peripheral speed of the squeeze rolls and the inside pressure. [59] US Pat. No. 6,447,278 B1 discloses a lateral routing of the double-layered film web directly after the take-off roller pair.

[60] US Pat. No. 4,086,045 again shows a cast film plant, which is therefore not of high relevance here because no treatment takes place above the rising heat from the extruder.

In US 3,768,949 an early embodiment of a reversing device is shown, wherein the withdrawal of the tubular film by two non-pressing single rollers takes place as a deduction, which still together constitute a deduction roller pair in a broader sense. [62] In US 3,340,565 rotatable cooling rollers are shown so that the cooling time can be adjusted continuously.

[63] US Pat. No. 3,1 16,787, in turn, shows a cast film system which, for lack of processing steps above the hot extruder, is a distant prior art.

[64] US Pat. No. 4,676,728 provides a reversing device with vertically standing turning bars or rollers. The same applies to US Pat. No. 5,727,723.

In DE 35 08 626 C l rollers for threading the incoming film tube when starting the blown film plant can be moved apart. Then, a comb-like operation of the turning bars and the guide rollers takes place against each other into an operating position. [66] Also in DE 692 08 002 T2 a longitudinal stretching of the film tube takes place only above a preliminary drawing roller, that is not after the withdrawal roller pair. In addition, heating is not carried out in the local cold-orientation zone.

[0002] In GB 2 201 371 A, a tubular film is first unrolled from a roll, then guided upwards above a blown film line, heated there, then guided vertically downwards and thereby inflated, and finally drawn off and wound up again. A heating after the pair of draw-off rollers is not provided, also is a hotter Blaskopf not provided, so that the resulting heat over it is not present and therefore unusable.

[0009] WO 2005/102666 A1 shows a blown film line in which either the distance between the pair of preliminary drawing rolls and the take-off roll pair is adjustable by means of a vertical adjusting mechanism, or in which a turntable with different rolls is provided, in both cases the Doppellagenfolienbahn after the pair of withdrawal rollers only laterally and then led down.

[69] Above the treatment roller track, a turning bar device may be provided, in particular within a reversing device. The reversing device ensures by means of a reversing twisting of turning bars and or rollers for a regular laying any unevenly thick spots of the film tube to a total quite uniform Aufwickelergebnis on the roll. A reversing unit can be taken, for example, from EP 0 673 750 A1.

[70] A reversing device should not be construed as a "treatment roller track" within the scope of the present patent application.

[71] In addition, a treatment roller track preferably exclusively comprises rollers, also conceivable are turning bars or other means for guiding or deflecting film.

[72] In addition, reversing does not include active heating for the double-layer film web.

[73] According to a second aspect of the present invention, the stated object solves a blown film plant, with a ring die for extruding a film tube, with a hose forming zone for longitudinal and transverse pulling of the film tube, with a coolant for moving in the machine direction film tube, with a flattening for the film tube to a double-layer film web and with a take-off roller pair beyond the coolant for removing the film tube, wherein beyond the take-off roller pair a treatment roller path to the longitudinal paths of the double-layer film web, optionally with a heating means, is provided for the double-layer film web, wherein the treatment roller track comprises a first draw roll and a second draw roll following the first draw roll, wherein the take-off roll pair is adapted to be driven at a take-off roll speed, and wherein the second draw roll is adapted thereto running at a stretching speed higher than the drawing roller speed and the speed of the first drawing roller so that, in operation of the blown film line, the double layer film web is stretched between the first and second draw rolls in the machine direction, wherein the blown film line is characterized in that Treatment roller path before and / or on the first draw roll a breakthrough of tensile force from the second draw roll on the pair of withdrawal rollers inhibiting punch-through brake is provided.

[74] It should be explained conceptually that the second draw roll, by virtue of its higher peripheral speed, exerts a tensile force on the double-layer film web tapering towards it. In the quasi-stationary production process, this tensile force follows the principle of "actio = reactio." Therefore, there must be a bearing for absorbing this tensile force in the counter-machine direction of the second draw roll However, the present invention has recognized that by far the maximum potential can not be extracted from a blown film line, because in order to be able to absorb the tensile force of the rapidly driven draw roll, the contact pressure of the take-off rolls must be quite high relative to one another However, if the nip contact force is increased in order to be able to absorb the tensile force from the rapidly driven draw roll, then this must not only depend on the temperature, but also on the pressure of the two film webs in the nip the film accordingly with a lower temperature through the Discharge roll nip be driven. If, however, the invention presented here is followed and the punch-through brake between the (possibly first, but in any case the second) faster than the take-off rollers driven draw roll is installed, then the reaching of the draw section on the take-off rolls tensile force is reduced or even eliminated. The contact pressure of the two take-off rolls in the withdrawal nip can then be set to a minimum and must ideally are dimensioned only on the basis of those parameters that prevail in the machine direction upstream of the take-off roller pair. Ideally, even no tensile force should reach the draw-off roller pair from the stretched section and must be stored there. [75] Various measures may be considered as "break-through brakes", not including simple passive roles, but at least the following three concrete implementations should be included:

[76] Thus, as the first of the three concrete variants, the traction brake can have a speed-controlled holding roller. This is understood to mean a roller whose speed, whereby the peripheral speed is always to be understood in the case of rollers, is infinitely or stepwise controllable. In particular, it is envisaged that the speed of the holding roller should be adjustable in relation to the speed of the second draw roller.

[77] The nip roll may be the first draw roll, but it may also be located before the first draw roll.

[78] The preferred embodiment provides that the holding roller is arranged directly above the take-off roller pair and the first and the second draw roller adjoin it. In such an embodiment, the first draw roll may either be passive, or it may be driven slower than the second draw roll regulated, especially at least approximately at the speed of the take-off roll pair.

[79] As a second concrete variant, it is envisaged that the traction brake has a pressure roller. A pressure roller makes it more difficult for the double-layer film web to slip around the surface of a roller. Thus, in a preferred embodiment, a pressure roller can be set against the holding roller. In a particularly preferred embodiment, even in such a constellation, the holding roller is the first roller of the treatment roller track and / or the last roller in front of the first stretching roller. The third concrete variant provides that the traction brake has a Umschlingungswinkelführung for wrapping a first roller within the treatment roller track with at least 160 °, preferably at least 180 °. The first roller is preferably the holding roller. As an alternative to the holding roller, it is conceivable to provide an optional heating roller, preferably laterally spaced from the roller follower from the holding roller and the two draw rollers, so that a foil web can be heated from two sides, first on a first side of the optional heating roller, then on its second side of the holding roller, which can be configured as a heating roller at the same time, which has a beneficial effect especially in thicker films. [81] It may be advantageous to achieve a lower overall height of the blown film unit to provide a transverse orientation for the rollers of the treatment roller section, wherein a "transverse" orientation should be present when the double-layered film web runs horizontally rather than vertically In view of the course of the film web around rollers or turning bars around the course can be defined by the actual film run and / or by the position of the axes of rotation of two rollers or turning bars to each other.

[82] In particular, it should be borne in mind that the paths connecting two, three, four, five, six or more reels are horizontal rather than vertical, either invariably or with exceptions between them.

[83] Two, three, four, five, six or more rolls should particularly preferably be arranged horizontally relative to one another.

[84] Although it is already known from US Pat. No. 6,413,346 B 1 to provide a treatment rolling section with a plurality of roller pairs and intermediate stretch sections in a transverse course to the vertical extrusion direction. The local pairs of rollers lie but exactly horizontal side of the pair of delivery rollers and then continue down to a winder. A turner bar unit is not disclosed in the document. That's why it does There sense to lead the film web to the side, because it finally has to be guided down.

[85] If a reversing device were present above the take-off roller pair in the document, then the film would have to arrive again above the take-off after the treatment roller path. This idea has hitherto prevented the system designers from leading the film web transversely, let alone horizontally, on the piece, which is anyway quite short, between take-off and reversing. Because each part of the path around which the film web is guided laterally, it must then be led back again, which makes a plurality of rollers necessary. [86] However, the present aspect has now recognized that it sometimes makes sense to provide a larger number of rollers and / or turner bars in a treatment roller track. However, a blown film line with a reversing unit builds significantly lower if the several rolls of the treatment roller line between the trigger and the reversing unit are arranged as horizontally as possible. With the lower height also a lower hall height is necessary, so that very significant costs can be saved.

[87] The treatment roller track can have a temperature control which allows the heating means to heat the double-layer film web at the entrance of the treatment roller section by less than 80 K, preferably by less than 30 K. [88] It does not matter if the control system is the current temperature for example on the double-layer film web picks up or on the roll surface when a heat roller is used. In practice, a variant is preferred in which the temperature of a fluid return from the roller is measured.

[89] Theoretically, even the control can do without a temperature sensor, because at a given temperature profile of the melt at the die and above it to the deduction is relatively well known with what temperature the double-layer film web enters the treatment roller track. [90] The clou of the heating means in the treatment roller track is to provide a heating, but only slightly above the incoming temperature of the double-layer film web.

[91] In general, it should be noted that the temperature data given in the context of the present patent application are to be understood as technical mean temperatures. In practice, the temperatures vary over the length of a roller, ie across the width of the film web, usually by at least 1 to 4 K.

[92] In this way, the energy balance of the blown film plant can be optimized: The cooling of the upwardly drawn film tube is adjusted so that it is just sufficiently cool when reaching the calibration basket and on the take-off rolls; He then passes through the mechanically critical point on the take-off roll, and then need only be heated by a very small amount to be easily stretched.

For example, polypropylene can be used for the films. In the endothermic process, ie during the melting and blowing, the melting occurs at about 160 ° C to 168 ° C. During the rise, that is, during the cooling of the film, however, the crystallization occurs at about 1 15 ° C to 135 ° C, on the other hand. Below these temperatures, the double-layer film web can be reliably squeezed from the pair of trigger rollers and thus pulled. After deduction roller pair then already sufficient heating by, for example, 10 K to 50 K in order not to bring the film back to the melting point, but still stretch the film web process reliable.

[94] It is further assumed, for example, that the room air temperature Tu is about 30 ° C. at the installation site of a blown film installation. Then the film web reaches in conventional systems, the stretch device so with about 30 ° C, usually with slightly higher temperature. Because of the strong air movement on the surface of the film web - due to the rapid forward movement of the film web - but a rapid drop in temperature of the film web is generally observed as soon as the film web is continued laterally after passing through the trigger. Because at the trigger the double-layer film web usually has a temperature between about 60 ° C and about 80 ° C. [95] For the planned stretching process in a flatness package, however, temperatures of around 80 ° C are usually sufficient. Temperatures around 85 ° C are usually sufficient for prestretching an MDO. And for stretching in the context of an MDO, temperatures ranging from 100 ° C to 105 ° C for polyethylene, from 130 ° C to 140 ° C for polypropylene and around 70 ° C for polyamide in the film web should prevail. Thus, just after the deduction, depending on the application, heating by only a few K is sufficient, or even a pure maintenance of the temperature, which is also made possible by a heating medium.

[96] In a particularly preferred embodiment, the treatment roller track has a heating roller for heating the double-layer foil web for easier treatment within the treatment roller path.

[97] A heat roller is a roller that mechanically engages the double-layer film web as soon as the blown film line is in operation. Along a predetermined portion of the roll surface, given by the wrap angle, the double-layer film web abuts against the heat roller. In particular, during this contact phase, a good heat flow from the heating roller on the film occurs.

The heating roller itself is preferably designed in its interior, for example as close as possible to the surface, as an active heating means.

[99] It can be provided that a heating roller is set up to produce a segmented temperature profile along its roll length. For example, a segmentation in two, three, four or more segments may be provided. The individual segments can be flowed through by different heating fluids, for example, or active heating means can be provided in or on the roller. If the roller can produce a segmented temperature profile, then the film can be imprinted with a specific temperature profile. [100] A heating station for the double-layer film web can also be designed differently than with a heating roller, for example with a heating section with heat radiators. [101] An analogous idea can also be applied to all of the following types of "reels", each of which is to be understood only as an example, albeit preferred, of "stations".

Preferably, the heating station, that is to say, in particular the heating roller, has a temperature meter in order to be able to be regulated within a predefinable temperature interval. This temperature interval should be adjustable so that the resulting temperature of the running double-layer film web is less than 80 K, preferably less than 30 K or 20 K, over that of the incoming double-layer film web.

[103] Using three examples, [104] For a flatness package in the treatment film section, for example, the feed temperature of the double-layer film web can be 60 ° C., ie a conventional temperature on the take-off roller pair. If a temperature of 80 ° C is desired for stretching as part of the flatness package, then the heating station is to heat the double-layer film web by only about 20 K. Compared with a conventional system in which the double-ply film web is first stretched on the hall floor, ie with a feed temperature to the flatness package of about 30 ° C, which requires a reheating of about 50 K, the amount of energy for reheating of 30 K is now saved ,

[105] It is proposed that the double-layer film web is temperature-elevated in the course of the heating roller between plus 5 K and plus 80 K; Preferred values are a. plus 5 K to plus 20 K for a flatness package, especially with a discharge temperature of about 80 ° C; b. plus 5 K to plus 25 K for a prestretchen, especially with about 85 ° C in the drain.

[106] It is proposed that the treatment roller track has a stretch section for longitudinal pulling of the double-layer film web. [107] It has already been explained above that a stretch portion is structurally implemented by first providing a nip roll or other holding means in the machine direction, whereupon the stretch portion has a draw roll on its machine downstream side, or a draw roll pair as explained above, for faster transport the double-layer film web as at the nip roll.

[108] For example, with the diameters of a holding roller and a draw roller of equal size, a higher rotational speed can be set on the draw roller and a lower rotational speed on the holding roller. Both cases deal with the amount of circumferential speed. Depending on how the film runs through the treatment roller track, a stretch section can be achieved both with rollers that are oriented in the same orientation and rollers that run in opposite directions. If the film crosses the direct connection of the two roll axes within the stretch section, then the rolls should run in the opposite direction, otherwise in the same direction of rotation. A stretch ratio within the stretch section is preferably 1: 2 to 1: 4, more preferably 1: 2 for pre-stretch film for agricultural use Generally, a stretch ratio in the stretch section is from 1: 2 to 1 : 10 to be regarded as advantageous, but in particular the initially mentioned framework of 1: 2 to 1: 4.

[1 10] A "stretch" ratio within the stretch section is more than 1: 1, but preferably only up to about 1: 1, 05.

[11 1] The holding roller can preferably take on two functions, that is, for example, be embodied by a heating roller or otherwise embody a heating station.

[1 12] In general, it should be noted that in the context of the present patent application, the indefinite number words "a", "two", etc. are not to be understood as "exactly one", "exactly two", etc., but in the normal case as indefinite article. A statement of the kind "a" two ... "etc. is therefore to be understood as" at least one "at least two ..." etc., unless it is clear from the respective context that only about "exactly one", " exactly two ", etc. are meant. [1 13] In a particularly far-reaching thought, even the take-off roll or the pair of take-off rolls, ideally in the form of a pair of squeegee rolls, can be the heating medium and possibly even serve as a holding roll at the same time. In general, however, this will lead to a worsened embodiment, because a heated take-off roller always carries the risk to heat the film even in the mechanical procedure of the removal already too much and thereby damage uncontrollably. Of course, the take-off roller pair also acts indirectly for the treatment roller track as a holding mechanism, because it specifies a certain, quite narrow speed range. Nevertheless, it is preferred for the reasons described above if at least one roller, which is transporting slowly relative to the draw roller, is provided as the holding roller between the take-off roller pair and the much faster transporting draw roller.

As such, the stretched section or stretch length may ideally have a length of at most 120 cm, in particular a length of at most 50 cm or 15 cm, especially at most 10 cm or 5 cm. It has been found in experiments by the inventors that the shortest possible stretch section is advantageous in order to keep a cross-necking of the double-layer film web as small as possible. On the other hand, it facilitates the threading of the double-layer film web when starting the system considerably when there is a clear distance of at least 5 cm between the rollers of the treatment roller track, preferably of at least 10 cm. The beginning of the film is then easier durchfädelbar between the rollers.

[1 16] It is considered preferable if at least one of the rollers forming the treatment roller path is movable or pivotable out of position to facilitate threading. This principle can be adopted without inventive step from US 4,086,045. [1 17] It is proposed that the treatment roller section after the stretch section have an annealing roller or a pair of tempering rollers or a differently designed tempering station for relaxing the double-layered foil track after stretching. Prototype experiments by the inventor have shown that a memory effect of the film stretched in the stretch direction in the machine direction can be significantly reduced if the stretch section is followed by a second active heating device, in particular in the form of a tempering station with an annealing roller. [1 19] The first tempering roll may also be represented by the draw roll, and / or one or more separate tempering rolls may be provided.

In the tempering path, the double-layer film web should assume a temperature between minus 5 K and up to plus 30 K, preferably between plus / minus 0 K and plus 20 K, in each case opposite to the temperature of the double-layer film web in the area of the strip.

[121] Particularly preferably, the draw roll is formed immediately as a first annealing roll, after which a first or even a second further tempering roll can follow.

[122] Preferably, a plurality of tempering rollers have the same temperature control, and are thus adjusted so that they impart the same temperature to the double-layer film web in the course. In practice, this is easily adjusted, for example, by accepting deviations, using a return flow of heating fluid adjusted to the same temperature.

[123] The idea of "the same temperature control" is not deviated from when successive rolls give slightly different temperatures of the double-layer film web, in particular in a fluctuation range of plus / minus 5 K or plus / minus 10 K.

[124] It may be desirable to selectively generate an ascending or descending temperature cascade in the double-layer film web by means of the heating and / or tempering rollers. In general, each station, that is to say in particular the heating station, tempering station and cooling station, can have several rollers to be passed through in succession from the double-layer film web. sen. This facilitates the adjustment of the film temperature to the desired values.

Finally, it is proposed that the treatment roller track has a cooling station for the double-layer film web, in particular a cooling roller, especially with an active coolant.

In the abovementioned temperature cascade, it is proposed that the cooling station of the double-layer film web impose a jump in temperature between minus 5 K and minus 80 K, in particular between -10 K and -20 K, in particular at about 60 ° C and / or approximately to room temperature and / or up to about 40 ° C to 60 ° C. An existing reversing process runs reliably even at foil temperatures of about 60 ° C.

[128] A cooling roller can already be regarded as a cooling roller if it has no active heating means. Preferably, however, it has an active coolant.

[129] In particular, a chill roll can have an explicit heat dissipation means, for example via a water circuit or another fluid circuit for a coolant, which is guided out into the chill roll and out of the chill roll by means of a line.

In a preferred embodiment, a heat exchanger, an electrically driven fluid pump and / or a cold pump are integrated into the circuit and connected to the cooling roller.

[131] The treatment roller track may advantageously have a control for a flatness improvement, wherein a longitudinal stretching of the double-layer film web is performed by 0.5% to 5%.

[132] Alternatively, the treatment roller track may have a control for stretching, with longitudinal stretching of the double-layer film web by more than 5, preferably more than 100%, or more than 500%. Above were already data to a possible configuration for stretching, that is MDO, with a draw ratio within the draw section of ideally from 1: 2 to 1:10, and or with a draw ratio from the holding roll to the cooling roll, ideally from 1: 2 to 1: 4th [133] In the above, possible temperature jumps between the running temperatures of the double-layered film web from the rolls or other formed stations within the treatment roll line have already been explained.

[134] Regardless of the above-mentioned further boundary conditions, it is proposed that the treatment roller track be a heat roller for the double-layer film web at a temperature level of plus / minus 0 K or plus 1 K to plus 80 K or more in the case of high-speed double-layer film webs, in particular polypropylene , in particular compared with the machine direction previous station and / or the roller temperature of the take-off roll.

Alternatively and cumulatively, it is proposed that the treatment roller section compare a draw roll for the double-layer film web with a temperature level of minus 10 K, preferably from plus 5 K to plus 30 K, or plus 50 K or more in the case of high-speed double-layer film webs with the machine direction previous station.

Alternatively and cumulatively, it is proposed that the treatment roller track compare an annealing roller for the double-layer film web with a temperature level of minus 10 K, preferably from plus 5 K to plus 30 K, or plus 50 K or more in the case of high-speed double-layer film webs with the machine direction previous station.

[137] Alternatively or cumulatively, it is proposed that the treatment roller track comprise a chill roll for the double-layer film web having a temperature level of minus 10 K to minus 80 K, or minus 100 K in the case of high-speed double-layer film webs, compared to the machine direction previous station. [138] In order to make the overall system as flat as possible, in particular if a reverberating unit is arranged above, it is proposed that the treatment roller section has two transversely oriented sections in the course of the double-layer foil path, preferably three transversely oriented sections, in particular one vertical climbing direction spanning the take-off roller pair.

[139] It has already been explained above that a "transversely" arranged orientation should already exist if, when viewed from the side of the rolls, ie parallel to the rotation axis orientation of the rolls, the direct connection between two successive rolls tends to be horizontal is as vertical, ie a maximum of 45 ° relative to the horizontal, preferably at most 30 °, more preferably at most 15 °, 10 ° or 5 °.

[140] Decisive for the overall height is less the running of the film than the arrangement of the individual rolls. The film can be designed to run on one side or the other depending on the given arrangement of the rolls, but because of their practically negligible thickness, they do not require any real height.

[141] It may even be advantageous if the film in the transverse sections is less horizontal than the connection between the two axis rollers.

[142] The above-described feature that a subsection spans a vertical climbing direction over the pair of take-off rolls is to be understood so that the film travel path provided between the two successive rolls intersects that virtual, vertically disposed plane which is above the nip of the take-off roll pair.

With such a design, therefore, rolls are arranged on both sides of the vertically upward-rising plane above the take-off roll pair, the film running across the pages, preferably reciprocating, so that a rather long film running distance is achieved for the treatment roll line, at the same time but the overall height is kept low. [144] A preferred embodiment of the invention provides that the treatment roller track has three equally transversely oriented sections, in particular spanning only once a vertical climbing direction over the pair of take-off rollers.

[145] In such an embodiment, for example, four rollers are arranged at least essentially in one line, namely in a line lying transversely to the ascent direction, preferably almost or exactly horizontally.

[146] For threading, the treatment roller track can have a threading aid with a displaceable or pivotable roller. This has already been explained. The combing depth is preferably adjustable to desired dimensions, so ideally electronically entered via a system control.

It should be expressly understood that cumulatively to the longitudinal stretching of the double-layer film web also transverse stretch can be provided, for example with divergently arranged guideways in which singular gripping means such as clips or needles are guided, which ultimately pull the film web transverse to the machine direction.

[148] According to a third aspect of the invention, the stated object solves a method for producing a blown film web in a blown film line, in particular in a blown film line as described above, with the steps

Extruding a film tube; - Inflating the film tube on a hose forming zone for cross pulling the

Film tube;

Cooling the ascending film tube with a coolant;

- laying the film tube to a double-layer film web with a flat lay; Pulling the double-layer film web with a pair of draw-off roller under longitudinal pulling of the film tube; the method being characterized by the further steps

Passing the double layer film web above the take-off roller pair further upwards and through a treatment roller path with a heating means to heat the double-layer film web; and

Treating the double-layer film web in the treatment roller track, in particular stretching the double-layer film web in a stretch section of the treatment roller track and / or

Guiding the double-layer film web within the treatment roller path around a first draw roller and a second draw roller following one of the first draw roller, the take-off roller pair being driven at a take-off roller speed, and the second draw roller being driven at a stretch speed higher than the take-up roller speed and as the speed of the first draw roll so that in operation of the blown film line (1) the double-layer film web is stretched between the first and second draw rolls in the machine direction, wherein within the treatment roll line before and / or on the first draw roll a traction from the second Stretching roller on the deduction roller pair inhibiting punch-through brake is provided so that the punch-through brake is a bearing for receiving the tensile force.

[149] It has already been explained above that these treatment steps are of great advantage. Due to the fact that the film in the form of the double-layer film web above the take-off rolls is guided further upwards, a long web guide is dispensed with. which avoids energy-consuming further cooling of the film after the take-off roller pair.

[150] The film can thus be brought from first heat with little additional energy to a better processed temperature level and then stretched for example, in particular stretched or stretched, or otherwise treated, for example, the surface can undergo treatment and / or the film can can be imprinted and / or components can be attached or inserted, such as active or passive vibration circuits, often referred to as RFID chips, and / or the film can be irradiated and / or the film can be laminated and / or it can Corona treatment of the surface can be performed and / or the film can be embossed and / or an adhesive can be applied and / or a lubricant can be applied and / or it can be applied and / or an anti-fog coating targeted tempering of the double layer film web to assist in the migration of aggregates w ground if aggregates are to migrate to the film surface to act there, so that a downstream tempering or storage can be omitted, the migration is essentially a function of temperature.

[151] And / or a targeted influence on shrinkage widths of the film can be made. By sufficiently tempering, the shrinkage after stretching can be reduced to producing a so-called "dead film" without shrinkage Alternatively, an increase of shrinkage values can be achieved, especially shrinkage in the machine direction, by deliberately "freezing" stresses.

[152] And / or there is a targeted adjustment of the curl to avoid curling in asymmetric film structures made.

[153] For the above applications, the method described here and the blown film line described here can be advantageously used selectively.

[154] For threading the double-layer film web during start-up of the blown film line, one or more rollers of the treatment roller section can be moved from its working position be moved or pivoted and the double-layer film web after threading by means of a back process or Rückverschwenkens be curious.

[155] Finally, according to a fourth aspect of the present invention, the stated object is achieved by a film produced by a blown film line and / or by a method as described above.

[156] Both the system and the process have a tangible and comprehensible effect on the finished film: it results in a particularly homogeneously biaxially stretched film if the molecules of the first heat are reheated immediately and then stretched instead of cooling down first allow.

[157] Thus, once the film has cooled down, it naturally has to be heated quite quickly to the desired high temperature range in order to be able to operate the blown film line economically, which will lead to the described film properties which are not uniformly predictable.

The quality of the film product produced by the proposed method is therefore also demonstrably advantageous on the film, provided that the parameters are suitably adjusted in the blown film production according to the present invention.

[159] The invention will be explained below with reference to six embodiments with reference to the drawings. Show there

FIG. 1 shows schematically in a vertical sectional plane perpendicular to a pair of withdrawal rollers a first variant of a treatment roller track with five rollers and a reversing device arranged above it,

FIG. 2 shows, in an otherwise unchanged view from FIG. 1, a second variant of a treatment roller track with five rollers and a reversing unit arranged above it, FIG. 3 shows, in an otherwise unchanged view from FIG. 1, a third variant of a treatment roller track with five rollers and a reversing unit arranged above it,

FIG. 4 shows schematically in a vertical sectional plane through a pair of withdrawal rollers a fourth variant of a treatment roller track with five

Rollers and an overlying reversing device, with a lower overall height, in particular as a design for an MDO unit,

5 shows schematically in a vertical sectional plane through a pair of withdrawal rollers a fifth variant of a treatment roller track with four

Rollers and an overlying reversing unit, in particular as a design for a flatness package, and

FIG. 6 shows very schematically a possible sixth variant for a treatment roller track with the lowest possible height, FIG. 7 shows a diagram for developing the longitudinal tensile stress σ over one

Longitudinal expansion ε of a plastic film,

8 shows schematically in a vertical sectional plane through a pair of take-off rollers a sixth variant of a treatment roller track with five rollers and a reversing unit arranged above and FIG. 9 schematically in a vertical sectional plane through a pair of take-off rollers a seventh variant of a treatment roller track with six rollers for four treatment stations and with one arranged above it reversing unit.

The blown film line 1 (shown only in the upper area) in FIG. 1 consists essentially of an extruder, a blow head with a ring slit nozzle, a riser section arranged above it for an extruded tubular film, a calibration basket, a Flattening and a pair of draw-off rollers 2 above the flattening, wherein a first take-off roller 3 is finely adjustable in position by a first holder 4, while a second take-off roller 5 is mounted horizontally displaceable by an adjusting cylinder 6 on a slide bearing holder 7. The adjusting cylinder 6 can thus move the second take-off roller 5 horizontally toward and away from the first take-off roller 3.

[161] Above the take-off roller pair 2, a treatment roller track 8 is provided. There are a total of five rollers, namely a first roller 9, a second roller 10, a third roller 1 1, a fourth roller 12 and a fifth roller 13th

[162] The five rollers of the treatment roller track 8 are arranged alternately on different sides of a virtual plane 14 which is parallel to central axes 15 (exemplified) of the two take-off rollers and extends vertically through the nip between the two take-off rollers. The virtual plane includes the area that would sweep the laid-flat film as the flattened film would simply rise vertically from the nip of the pick-up rollers. In the vertical section perpendicular to the central axes 15, the virtual plane 14 therefore presents itself as a vertically extending line, namely following the vertical climbing direction of the film and starting at the nip of the take-off roller pair.

[163] The first roller 9, the third roller 11 and the fifth roller 13 lie on a first side 16 of the virtual plane 14; on the other hand, the second roller 10 and the fourth roller 12 lie on an opposite second side 17 of the virtual plane 14.

[164] At the same time, all five rollers of the treatment roller track 8 are set close to each other in the vertical so that each overlap of the first roller 9 with the second roller 10, the second roller 10 with a horizontal projection of the rollers on the virtual plane 14 the third roller 1 1, the third roller 1 1 with the fourth roller 12 and the fourth roller 12 with the fifth roller 13 results, each about one third of the total diameter size of the five rollers. [165] The first four rollers 9, 10, 11, 12 of the treatment roller track 8 are of equal size, while the two take-off rollers 3, 5 of the pair of delivery rollers 2 and the fifth roller 13 are made larger.

Distances 18 (identified by way of example) of the five rolls of the treatment roll section 8 with one another are in each case at least 50 mm.

[167] The first roller 9 is provided with a speed control, so that its surface speed can be adjusted quite accurately to a predetermined level during a rotation.

The second roller 10 is provided with a drive and a control which can adjust the second roller 10 to a significantly higher peripheral speed than the first roller 9.

[169] The third and fourth rolls 11, 12 may be drivable, for example at the same speed as the second roll 10 or, preferably, slower than the second roll 10. [170] The fifth roll 13 may also be drivable, for example at least substantially at the same speed as the fourth roller 12 or, preferably, slower than the fourth roller 12.

[171] It should be noted that it may be advantageous to slow down after stretching to relieve stresses in the film. The first roller 9 is also provided with an active heating means and a temperature sensor (both not shown), namely a tube guide for a heating fluid with a heat conductive connection to the surface of the first roller 9, while the temperature sensor either via a non-contact measurement of the surface temperature the first roller 9 and / or the running double-layer film web can detect. [173] Preferably, the temperature sensor is arranged in a return of the heating fluid, so that, assuming a certain inaccuracy, it can be assumed that the film will run somewhat cooler than the return temperature of the heating fluid.

[174] Ideally, the discharge temperature of a double-layer film web assumes exactly the temperature of the roll surface. In practice, however, the draining film will usually be a little warmer or cooler, depending on whether it was cooled by the roller or heated.

[175] The person skilled in the art can measure the running temperatures of the film from the individual rollers, for example, contactlessly by means of an infrared sensor, and adjust the roller temperatures based on the actual film temperatures in a particularly precise embodiment.

[176] The second roller 10, the third roller 11 and the fourth roller 12 may each independently be provided with such an active heating means as well.

In any case, a roller, here the fifth roller 13, is equipped with a temperature measurement and an active coolant.

Above the treatment roller track 8, two non-driven deflecting rollers 19 (identified by way of example) are arranged on the way to a reversing unit 20 arranged above the take-off roller pair 2 and the treatment roller track 8, wherein the guide rollers 19 and the reversing unit 20 from the prior art suffice are known and should therefore not be explained further here.

[179] Both the take-off rolls 3, 5 of the take-off roll pair 2 and the five treatment rolls of the treatment roll section 8 and, finally, the guide rolls 19 are mounted on their front sides on a machine frame 21.

[180] Two temperature control devices 22 (identified by way of example) are provided on the side of the machine frame 21. With the tempering devices 22, the tempered rollers of the treatment roller track 8 are preferred via coolant lines or heat transfer lines. also connected via temperature sensor data lines (not shown). Contained in the temperature control 22 or at least in access to the temperature control 22 electronic microcontroller (not shown) are provided, which nen can make the set control of the temperature of the tempered rollers on the basis of the fluid return.

[181] In operation of the blown film line 1, a film tube (not shown) is extruded from the extruder (not shown) through the annular slot die (not shown). The film tube is pulled up the blown film line 1, through the calibration basket (not shown) and the flattening (not shown). At the end of the flattening of the film tube is largely laid flat and runs in this form in the take-off roller pair 2 a. From there, talk of a double-layer film web 23.

The double-layer film web 23 can optionally be guided in a straight ascent direction above the take-off roller pair 2, congruent with the virtual plane 14, between the rollers 9, 10, 11, 12, 13 of the treatment roller track 8 and immediately onto the guide rollers 19 and be led from there to the reversing unit 20.

[183] In this case, the blown film plant 1 corresponds to a conventional blown film plant. The reversing unit rotates during operation of the blown film line 1 and thus generates on a roll (not shown) at the bottom of the set-up surface (not shown) a film roll to be wound up as uniformly as possible. [184] In an alternative - and here preferred - film guide web, however, the double-layer film web 23 runs around the five rollers 9, 10, 11, 12, 13 of the treatment roller track 8, in each case due to the geometry of the rollers to each other on the second roller 10, the third roller 1 1 and the fourth roller 12 results in a wrap angle of more than 180 °. The wrap angle of the first roller 9 depends in particular on the positioning height of the first roller 9 with respect to the pair of delivery rollers 2, and on the diameters of the three rollers and also on the distance of the first roller 9 to the virtual plane 14. In the arrangement selected here, the wrap angle at the first roller 9 about 170 °. [185] The same applies to the fifth roller 13, in which case in particular the positioning relative to the virtual plane 14, the first deflection roller 19 and the diameter between the fifth roller 13 and the first deflection roller 19 are relevant.

[186] In the described configuration, the double-layer film web 23 then passes in the extrusion direction, ie in the machine direction, up through the pair of take-off rollers 2 and from there initially clockwise (all information to the clockwise or counterclockwise direction refer to the sectional plane view of the figures) the first roller 9 led around. The first roller 9 serves as a holding roller. At the same time, the first roller 9 is flowed through by a first of a total of three heat or coolant circuits within the treatment roller track 8, namely a heating circuit.

In a configuration of the first variant of the blown film line 1 in Figure 1, the double-layer film web 23, for example, come with a film inlet temperature of about 60 ° C to about 80 ° C from deduction roller pair 2.

The first roller 9 is adjusted in such a way that its peripheral speed is the same as that of the double-layer film web 23, also in the pair of take-off rollers 2. In the distance between the pair of delivery rollers 2 and the first roller 9, the double-layer film web 23 therefore experiences no mechanical influence.

[189] Because of the high wrap angle of the double-ply film web 23 around the first roll 9, the double-ply film web 23 runs on the first roll 9 with adhesive friction, thus exactly at the same speed as the roll surface, even if the static friction is not present over the entire wrap angle ,

[190] The first temperature circuit, ie the heating circuit which passes through the first roller 9 in its function as a holding roller, is set, for example, to a temperature difference in the film between plus 5 K and plus 10 K, based on the film temperature at the outlet from the preceding first take-off roll 3. The double-layer film web 23 is thus heated when circulating the first roller 9 about 5 K to 10 K. Even this small temperature difference is sufficient to increase the processability of the double-layer film web 23 significantly, because the blown film plant 1 is (below 1) so that the film cools only in the course of the ascent and thus has a temperature anyway when passing through the two take-off rolls 3, 5, which is quite high, in the example tested between 60 ° C and 80 ° C. [191] With only very little energy, which must be provided by the temperature control unit 22, the foil can thus be rapidly brought back to a very good processable temperature level from the first heat in order to facilitate longitudinal decay.

[192] The second roller 10 is formed in the illustrated embodiment as a stretching roller. It has been driven in the positive tests with three to four times the circumferential speed in relation to the first roller 9. For stretching ratios which were more likely to go to 1: 3, a film quality which appeared more suitable for silage prestretching resulted; on the other hand, with a higher stretch ratio, ie rather in the direction of 1: 4 or beyond, a broader processability resulted, in particular with regard to the optical film qualities. [193] The second roll 10, that is to say the stretching roll, was provided in the positive tests as the first of a total of three rolls of a second temperature cycle, namely an annealing cycle. The annealing circuit flows through the second roller 10, the third roller 1 1 and the fourth roller 12. The temperature in the return of the annealing circuit was set to plus 5 K to plus 20 K with respect to the return of the preceding first roller 9, ie the holding roller.

[194] Thus, the second roller 10 carries two functions: It is on the one hand stretching roller, on the other hand annealing station in the form of an annealing roller.

The third roller 1 1 and the fourth roller 12 are formed as annealing rolls, so keep the reasonably high temperature level of the stretching roller in any case and thereby lead to a relaxation of the stretched double-layer film web 23, which helped to minimize a memory effect of otherwise occurring shrinkback , [196] The fifth roller 13, configured as a cooling roller, is connected to the third of the three temperature circuits, namely a cooling circuit. The temperature level in the return of the cooling circuit was ideally between minus 10 K and minus 20 K compared to the return of the preceding roller, so the last tempering.

[197] On all five rolls of the treatment roller track 8, the double-layer film web 23 runs predominantly with stiction. Ideally, therefore, the five rollers are surface-coated, in particular, thought of a spiral look or a silicone coating.

[198] It is understood that at least one application roller or pressure roller can be provided for each roller. In the prototype tests, however, driving without application rollers has already proven to be sufficient.

[199] Water has proven itself as the heating and cooling medium for the temperature control units 22 and the three temperature control circuits.

[200] In the outlet, the blown film unit 1 was driven at a film speed between 94 m / min and 340 m / min, and with a draw ratio between the first roller 9 and the fifth roller 13 between 1: 2 and 1: 3, again lower draw ratio, so rather going to 1: 2, more suited for silage-prestretch products appeared.

[201] In realizing the various aspects of the invention, the blown film unit 1 above the take-off roller pair 2 provides a treatment roller path 8 with a heating means for the double-layer film web 23, namely with the heated fluid circuit in the first roller 9 and additionally with the annealing circuit in the second roller 10, in FIG the third roller 1 1 and in the fourth roller 12th

In this case, therefore, even several active heating means are provided for the double-layer film web 23, namely a total of four different rolls.

[203] The provision of a heating medium in several rolls, at least in two rolls, especially with two different fluid circuits, also represents an advantage in itself. [204] In realization of the second aspect of the invention, a transversely oriented treatment roller path is provided above the pair of take-off rollers 2, since roller to roller within the treatment roller path 8, the rollers are approximately at an angle of 35 ° to 40 ° relative to the horizontal, are so aligned horizontally rather than vertically. The result of this is that because of their sufficient lateral offset, the rolls can be arranged so low that, in the case of a projection, they result in overlapping of the virtual plane 14, that is to say, build a total of less than the addition of the diameter of the five rolls.

[205] In the second variant of a blown film installation Γ in FIG. 2, the installation can be identical or similar to the take-off roller pair 2.

Above the take-off roller pair 2 and below the reversing unit 20, five rollers are again arranged, namely a first roller 9 ', a second roller 10', a third roller 1 ', a fourth roller 12' and a fifth roller 13 ' then a deflection roller 19 is provided above. [207] The five rollers perform the same function as described in the first variant of Figure 1, also the same three temperature control circuits are present.

However, in the second variant, the second roller 10 'and the fourth roller 12' are arranged on the same side of the virtual plane 14 as the first roller 9 ', the third roller 1 1' and the fifth roller 13 '. Thus, all rollers are arranged on the same side of the virtual plane 14.

A direct connection between the nip of the take-off roller pair 2 and the deflecting roller 19 is free, so that the double-layer film web 23 can optionally be guided upwards directly without ascending the rollers in the treatment roller path 8 in a rising direction. [210] Preferably, however, this variant is also designed as an MDO system, ie for longitudinal stretching of the film beyond the plastic flow of the double-layer film web 23. [21 1] The five rollers of the treatment roller track 8 have a very small clearance, which in any case is less than 5 cm. When the blown film unit 1 'starts up, it is therefore very difficult to thread the film between them in the illustrated operating position of the rollers of the treatment roller track 8, even if the rollers are driven in opposite directions of rotation to their predecessor.

For threading a start (not shown) of the double-layer film web 23, therefore, two rolls, namely the second roll 10 'and the fourth roll 12', can be moved to the left, that is to say on the opposite side of the virtual plane 14. The double-layer film web 23 can then simply vertically threaded through the five rollers, then the second roller 10 'and the fourth roller 12' are again driven on the same side 17 of the virtual plane 14 as the remaining three rollers are positioned, and the extrusion process can be considered steady state Process are driven.

Preferably, the second roller 10 ^' can optionally be adjusted to the imaginary plane from the axes of the rollers 9 ^' , 1 Γ, 13 ^' or even beyond, resulting in a continuously adjustable stretch section. In preliminary tests, an adjustability of the stretch length has shown to be favorable in terms of process technology, for example because a higher fault tolerance compared to defects resulted when passing through the imaginary plane.

[214] In the threading position of the second roll 10 ^' and the fourth roll 12 ^' , the blown film plant 1 ^' can be operated like a conventional blown film plant.

[215] In the third variant of a blown film line 1 "in FIG. 3, substantially the same structure as in the second variant of the blown film line in FIG. 2 is selected, but the five rolls of the treatment roller section 8" are all located on the first side 16 of the virtual plane 14. Since an entry side into the reversing unit 20 is also located on the first side 16 of the virtual plane 14, it is possible to directly pass from the fifth roller 13 "to the reversing unit 20. A deflecting roller 19 is not necessary. The second roller 13 "is also arranged opposite to the four preceding rollers so that its edge facing the virtual plane 14 protrudes beyond the preceding four rollers so that the double-layer film web 23 without threading and without passing through the treatment roller path 8 to the four The wrapping angle of the double-layer film web 23 around the fifth roller 13 "is still almost 90 ° without threading, even almost 180 ° in the threaded state, so that sufficient guidance is ensured.

In the third variant of the blown film line 1 "in FIG. 3-as in the second variant of the blown film line 2 of FIG. 2-a combing of the second and fourth rolls is provided, so that the start of filming during start-up of the strip is effected with a simple straight pass Attachment can be threaded.

The fourth embodiment of the blown film system Γ "in FIG. 4 is also identical to a pair of take-off rollers 2" ', as are the variants described above. [219] The first take-off roll 3 "', which lies on the same side 16 as the inlet into the reversing unit 20, is however displaceable in the fourth variant of the blown film plant Γ" for threading and for closing the take-off roll pair 2 "' second take-off roll 5 "', which lies on an opposite side 17 of the virtual plane 14, designed in principle fixed. [220] Above the take-off roller pair 2 "', four rollers of a treatment roller path 8"' lie side by side in a horizontal arrangement, and a fifth roller 13 "'is displaced laterally and in height thereto.

With regard to the virtual plane 14 above the take-off roller pair 2 "'are thus three rollers of the treatment roller track 8"' on the second, right here, page 17, whereas two rollers of the treatment roller track 8 "'on the first, here left , Side of the virtual plane 14, ie on the same side as the inlet to the reversing unit 20. A machine frame 21 "'for the rollers of the treatment roller track 8"' for this purpose has a cantilever 24 which protrudes laterally relative to a main body of the machine frame 2 "." The first roller 9 "" is mounted on the cantilever 24.

[223] Due to the horizontal arrangement of several rolls of the treatment roller track 8 "'side by side, here of a total of four rollers of the treatment roller track 8"', the blown film plant Γ "builds very low overall, although above the pair of take-off rollers 2" 'and the treatment roller track 8 "' nor the reversing unit 20 is arranged.

[224] Two of the rollers within the treatment roller track 8 "', in this case the second roller 10"' and the fourth roller 12 "', are again designed to be meshingly displaceable, so that threading into the system during startup is facilitated However, space can also be provided a pivoting, so for example, the second roller 10 "'around the first roller 9"' around be pivotable, while the fourth roller 12 "', for example, to the fifth roller 13"' or to the third roller 1 Γ "swivel around.

In a straight extension above the take-off roller pair 2 '", ie in the virtual plane 14, a straight running path 25 is left open for the double-layer film web 23, so that the double-layer film web 23 can also be produced without passing through the MDO-treatment roller path 8"' , It then runs straight up to a Geradlaufwegumlenkwalze 26 and from there into an inlet 27 of the reversing unit 20th

Alternatively, the double-layer film web 23 can be guided along an MDO travel path 28, which pivots directly into the virtual plane 14 opposite the inlet 27 and runs around the first roller 9 "'on the outside previously described pass through the other four rollers, which also have the same functions as described above. [227] From the fifth roller 13 '', the double-layered film web 23 finally runs, either via a further deflection roller 29 or directly, when the looping of the fifth roller 13 '' is already sufficient, to the inlet 27 of the reversing unit 20.

The fifth roller 13 "'serving as a cooling roller and / or a further deflection roller 29, such as further cooling units, can be adjustable with each other or against each other, individually or jointly, so that the cooling path is easily adjustable the fifth roller 13 "'and the further guide roller 29 can be mounted together on the machine frame, which rotates about an axis which is parallel to the axis of the illustrated rollers; or, for example, the further deflecting roller 29 can be moved or pivoted vertically downwards, so that the wrapping angle of the double-layer film web 23 can be adjusted on the MDO path 28 about the fifth roller 13 "'with relatively simple movements and can be dispensed virtually continuously predetermined cooling temperature, it is then possible to adjust the cooling effect before the inlet of the double-layer film web 23 in the reversing unit 20.

[229] A similar idea can be carried out, for example, with the first roller 9 ", which ideally serves as a holding roller and at the same time as a heating roller, which can also be adjusted in height or laterally so that the changed geometry of the MDO travel path give the double-layer film web 23 a changed wrap angle around the first roller 9 "'and an altered stretch length.

[230] A similar effect can also be achieved with a further pressure roller provided there.

[231] In the fifth variant of the blown film line 1 "", once again, above a take-off roller pair 2, there is a flat-lay track 30 and above it a reversing unit 20 with an inlet 27.

[232] Within the planishing section 30, a first roller 31, a second roller 31, a third roller 33, and a fourth roller 34 are provided. From there is a designated one Film run over a number of passive guide rollers 35 (first exemplified) to the inlet 27 provided in the reversing unit 20.

[233] The four rollers of the flatness path 30 are again provided laterally spaced from the virtual plane 14, so that a straight path 25 for the double-layer film web 23 results from the pair of take-off rollers 2 directly to the first passive deflection roller 35 and from there to the reversing unit 20 when the double-layer film web 23 is not to pass through the flatness system.

[234] Alternatively, the double-layer film web 23 - here for example around a first deflection 36 - are guided to the first roller 31, from there to the roller 32, from there to the third roller 33 and finally to the fourth roller 34, to the double-layer film web 23 also on this flat-lay path 37 einschert again in the straight path 25.

[235] In each case, two of the four rollers of the flatness track 30 are essentially at the same height, they each form a pair with a low overall height. When projecting onto the virtual plane 14, an overlapping area between the first roller 31 and the second roller 32 and even a congruence between the third roller 33 and the fourth roller 34 results.

[236] However, even a slight overlap is sufficient to achieve a lower height compared to a structure as shown in Figures 2 and 3. [237] All four rolls of the flatness stretch 30 ideally have a pressure roll 38 (identified by way of example), which are each pressed in an articulated manner with a pressure arm 39 (identified by way of example) into the respective roll.

[238] In the present embodiment, pressure rollers are provided only on two of the rollers, namely on the first roller 31, which serves as a holding roller and heat roller, and the second roller 32, which serves as a stretching roller and annealing roller. [239] Thus, between the first roller 31 and the second roller 32 results in a Dehnabschnitt 40, and at the circumference of the first roller 31 and the second roller 32 produces high tangential forces.

[240] On the other hand, the third roller 33 and the fourth roller 34, performed as chill rolls, are set in accordance with the surface speed of the second roller 32 so that no strain occurs there, or even more slowly, so that relaxation occurs can.

[241] The described embodiment is intended as a flatness package, that is usually with a maximum draw of 1: 1.05. The stretch length is quite long compared to the MDO variants.

[242] The resulting longer residence time in the stretch section is advantageous for a broad process window.

[243] Because only small draws are made, small drive powers are sufficient. Also individual drives are unnecessary, since the film worked only minimally. It is therefore sufficient if the holding roller and the second roller 32 are each driven and their speed can be controlled.

[244] Since only a low temperature and thus energy level must be achieved, a water heater according to the prototype experiments of the inventor is completely sufficient.

[245] In the flat sheet package, the second roll preferably has the same temperature as the first roll. The first roller serves as a heating and holding roller. The second roller serves as a stretching and tempering roller. The distance between the second and the subsequent third roller is then an annealing section.

[246] On the other hand, in an MDO embodiment, a draw of 1:10 or even more is readily possible. [247] The stretching length should be as short as possible in order to reduce the transverse contraction, the so-called neck-in. [248] The process control is much more critical because only a very short residence time can be recorded in the very short stretching nip.

[249] Since more rolls have to be tempered, a higher energy input is required and a relatively long tempering distance is necessary. [250] The drives must be kept strong enough to overcome the yield strength of the plastic and to slightly exceed the flow range.

[251] Single drives are proposed to allow individual process control.

[252] For a simple flatness improvement, an MDO design is actually too large and thus normally uneconomical.

[253] Since high temperatures are required for the MDO, it is normally proposed to use an oil heater.

Also in the fifth embodiment variant in FIG. 6, a transverse processing path is provided above the take-off roller pair, specifically a horizontally lying one for four rollers, wherein a chill roller is arranged further upwards and would permit a straight feedthrough of the double-layer foil web above the take-off roller pair.

Within the horizontally lying roller track, two rollers are again movable, namely a second roller pivotable about the first roller, and a fourth roller displaceable or pivotable and arranged on the other side of the virtual plane 14.

[256] Incidentally, the fifth variant on FIG. 6, just like the variants described above, can be used in a blown film line.

[257] Fundamental to the behavior of the films to be processed here is a graphic explanation in the diagram in FIG. 7. The longitudinal strain ε of the film is plotted on an abscissa 41, whereas the ordinate 42 on the other hand shows the longitudinal stress within the film, that is to say a variable proportional to the longitudinal tensile force within the film. The longitudinal stress is designated by the letter σ. Starting from a zero point 43, the film usually behaves with increasing longitudinal strain ε in a linear stress-increasing field 44. From a certain longitudinal strain ε ^* or associated stress σ ^* , the foil leaves the region of linear tension increase and the stress curve flattens that is, has a smaller pitch than the abscissa 41. [260] Starting from the longitudinal strain ε ^* , introduced longitudinal strains are irreversible.

[261] The stress σ then assumes a first maximum 45. At this point, the so-called plastic flow of the film begins. The associated longitudinal strain e ^Slreck is referred to as yield strength. A flow region 46 extends from the first maximum 45 of the longitudinal stress σ, referred to as σ stretch *, up to that region of the then rising branch 47, where the longitudinal stress σ again reaches the stress σ stretch.

[262] From there, the longitudinal stress σ increases steadily again with increasing longitudinal expansion ε, until a sudden failure in the form of a foil tear 48 occurs.

[263] In contrast, a flatness pact working range is in the range beyond the linear stress-increasing field 44, but below the yield strength g of ^stretch . In the linear stress-increasing field 44, ie up to the longitudinal strain ε ^* , the foil behaves elastically.

[265] In simple words, stretching a flatness package takes place between ε ^* and the local maximum. On the other hand, the stretching of an MDO takes place after the reunion of o ^Slreck . The treatment roller track 50 in FIG. 8, in its construction with five rollers, corresponds in principle to the second variant from FIG. 2 and the third variant from FIG. 3, but includes three with its first roller 51, its third roller 52 and its fifth roller 53 meshing rolls while their second roll 54 and fourth roll 55 are fixedly rotating.

For threading the double-layer film web at the beginning of a blowing process, the three intermeshing rolls, ie the first roll 52, the third roll 52 and the fifth roll 53, are moved out of their combed position, ie, to the left of the virtual plane 14 in FIG so that the double-layer film web from a nip 56 of the pair of withdrawal rollers 57 can simply be guided vertically upwards to a deflection roller 58. The deflection roller 58 is the first roller which lies beyond the treatment roller path 50. From the deflection roller 58, the double-layer film web is guided transversely, towards an inlet 59 into a reversing unit 60.

[268] During combing, the first roller 51 can not only be moved into the plane of the stationary rollers, ie second roller 54 and fourth roller 55 (shown in FIG. 8 by a first contour 61 of the scarfed first roller 51); Rather, the first roller 51 may even be passed through this plane by meshing, so that the central axis of the first roller 51 moves beyond the plane which is formed by the center axes of the second roller 54 and the fourth roller 55. The first roller 51 can thus assume a combed position for the blowing operation (represented in FIG. 8 by a second contour 62 of the first roller 51).

[269] In prototype tests, it has been found that a preferably infinitely variable adjustability of the combing depth, in particular with a combing depth through the plane of the stationary rolls, can be advantageous for process reliability and the resulting film quality.

[270] The treatment roller path 63 according to the seventh variant in FIG. 9 shows a somewhat different structure: [271] Above the squeezing roller pair 64, the treatment roller track 63 is in a vertical orientation.

[272] A first roller 65 is constructed as a heating roller and at the same time as a holding roller. It can be moved through the virtual plane 14 by meshing. The combing has already been described several times above. Its advantages and also the possibility of combing through the plane of the static rollers are now assumed to be known.

[273] A second roller 66 is provided with a significantly smaller diameter than the first roller 65. [274] A third roller 67 is also provided with a smaller diameter than the first roller 65, preferably as constructed herein with the same diameter as the second roller 66th

[275] The second roller 66 and the third roller 67 form a stretching station in which the third roller 67 is meshed. Due to the stepless adjustability of at least one of the two rollers 66, 67 of the stretching station, the stretching length can be infinitely adjusted, which has proven to be very advantageous in prototype tests.

[276] The second roller 66, which simultaneously constitutes a first roller of the stretching station, is preferably driven at a same peripheral speed as the first roller 65, that is, like the large holding roller. With regard to the function of the holding station, the second roller 66, rather than the stretching station, would actually be attributable to the holding station, together with the first roller 65. Only in terms of its diameter it is also possible for the second roller 66 together with the third roller 67 of FIG Add stretching station.

[277] The two small rollers, ie the second roller 66 and the third roller 67, are not heated but driven. This makes it possible to construct the second roller 66 and the third roller 67 with a very small diameter. However, the third roller 67 is driven at a higher peripheral speed than the second roller 66. Between the second roller 66 and the third roller 67, therefore, a stretch portion for the double-layered film web is formed.

[279] Assuming that at the given geometrical conditions, there is friction about 70 ° around the circumference of the faster driven third roller 67, the stretch length of the stretch section will be between about 250 mm to 290 mm and small roller diameters for large roller diameters between 100 mm and 140 mm approx. 15 cm to 19 cm, in concrete with a prototype approx. 17 cm.

Following the faster driven third roller 67, a first annealing roller 68 and a second annealing roller 69 are provided in the treatment roller path 63, the latter also being able to be meshed in its working position.

[281] The two tempering rollers 68, 69 are followed by a cooling roller 70, slightly enlarged in diameter in this example. The cooling roller 70 has a contact roller 71. [282] The cooling roller 70, together with its application roller 71, forms the last station of the treatment roller path 63. From there, the double-layer film web is led to the inlet for reversing.

[283] The rollers of the treatment roller track 63 are arranged quite close to each other, with a clearance in a vertical arrangement of only about 10 mm to 30 mm in order to achieve the lowest possible height.

[284] Preferably, several or even all roll surfaces of the treatment roller track 63 have a rough, non-slip surface, ideally with incorporated silicone. LIST OF REFERENCE NUMBERS

1 blown film line

2 take-off roller pair

3 first take-off roll

4 first holder

5 second take-off roll

6 adjusting cylinders

7 Guided bearing holder

8 treatment roller track

9 first roller

10 second roller

1 1 third roller

12 fourth roller

13 fifth roller

14 virtual level

15 central axis

16 first page

17 opposite second page

18 distance

19 guide rollers

20 reversing unit

21 machine frame

22 temperature control units

23 double-layer film web 24 cantilever

25 straight track

26 straight track deflection roller

27 enema

28 MDO track

29 further deflection roller

30 Planlege range

31 first roller

32 second roller

33 third roller

34 fourth roller

35 passive deflection roller

36 first diversion

37 Flat track

38 pressure roller

39 pressing arm

40 flatness stretch section

41 abscissa

42 ordinates

43 zero point

44 linear voltage increase field

45 first maximum

46 flow area

47 rising branch

48 foil tear MDO workspace

Treatment roller track first roller

third roller

fifth roller

second roller

fourth roller

nip

Off rollers

deflecting

enema

Reversing unit first contour

second contour

Treatment rolling line

Nipper roller first roller

second roller

third roller

first tempering roller second tempering roller

chill roll

contacting roller

Claims

claims:

A blown film line (1) having a ring die for extruding a film tube, a hose forming zone for longitudinally and transversely pulling the film tube, a coolant for the film tube moving in the machine direction, a flattener for the film tube to a double layer film web, and a pair of take-off rolls beyond the coolant for withdrawing the film tube, wherein in the machine direction beyond the take-off roller pair (2) a treatment roller path (8) for longitudinal stretching of the double-layer film web, characterized in that the machine direction is vertically oriented from bottom to top and the treatment roller path (8) above the take-off roller pair is, wherein preferably a heating means for the double-layer film web (23) is provided.

2. blown film plant (1), with a ring die for extruding a film tube, with a hose forming zone for longitudinal and transverse pulling of the film tube, with a coolant for moving in the machine direction film tube, with a flattening for the film tube to a double-layer film web and with a pair of withdrawal rollers beyond the coolant for removing the film tube, wherein beyond the withdrawal roller pair (2) a treatment roller path (8) is provided for the longitudinal stretching of the double-layer film web, the treatment roller path having a first draw roller and a second draw roller following the first draw roller, wherein the pair of take-off rollers is adapted to be driven at a take-off roll speed, and wherein the second draw roll to a is directed to run at a stretching speed which is higher than the take-off roll speed and the speed of the first draw roll so that during operation of the blown film line (1) the double-layer film web is stretched between the first and the second draw rolls in the machine direction, in particular blown film line ( 1) according to claim 1, characterized in that a breakthrough of tensile force from the second draw roll to the take-off roller pair inhibiting punch-through brake is provided within the treatment roller path before and / or on the first draw roll.

Blown film plant according to claim 2, characterized in that the punch-through brake has a speed-controlled holding roller.

Blown film installation according to claim 3, characterized in that the holding roller is provided with a speed control, which is set closer to the take-off roller speed is set up as to the stretching speed, in particular to regulate the take-off roller speed.

Blown film plant according to one of claims 2 to 4, characterized in that the punch-through brake has a pressure roller.

Blown film plant according to one of claims 2 to 5, characterized in that the punch-through brake has a Umschlingungswinkelführung for wrapping a first roller within the treatment roller track with at least 160 ⁰ , preferably more than 180 ⁰ has.

7. Blown film installation according to one of the preceding claims, characterized in that a heating section is provided in front of the first stretching roller, wherein in particular all the rollers are actively heated before the first stretching roller, especially exactly one holding roller and a separate heating roller.

8. Blown film installation according to one of the preceding claims, characterized in that above the treatment roller track (8) a reversing device (20) is provided.

9. Blown film installation according to one of the preceding claims, characterized in that the treatment roller track has a temperature control, wherein the heating means can heat the double-layer film web at the outset by less than 80 K, preferably less than 30 K.

10. Blown film installation according to one of the preceding claims, characterized in that the treatment roller track has a heating roller for heating the double-layer film web for easier treatment within the treatment roller track.

1. Blown film installation according to one of the preceding claims, characterized in that the treatment roller track has a stretch section for a longitudinal stretch of the double-layer film web, with a stretch region having a length of at most 120 cm, in particular with a length of at most 50 cm or 15 cm, especially not more than 10 cm or 5 cm.

12. blown film according to claim 10 or 1 1, characterized in that the treatment roller track after the stretched section has an annealing roller for relaxing the double-layer film web after stretching.

13. blown film installation according to one of the preceding claims, characterized in that the tempering roller has a tempering, which the doping pellet film can be heated by less than 30 K, in particular by less than 20 K.

14. Blown film installation according to one of the preceding claims, characterized in that the treatment roller track comprises a coolant for the double-layer film web, in particular a cooling roller.

15. blown film installation according to one of the preceding claims, characterized in that the treatment roller track has a control for a flatness improvement, ie with a stretching of the double-layer film web by 0.5% to 5%.

16. blown film installation according to one of the preceding claims, characterized in that the treatment roller track has a control for a Verre- ckung, ie with a stretching of the double-layer film web by more than 5%, preferably more than 100% or more than 200%, 300th % or 500%.

17. blown film installation according to one of the preceding claims, characterized in that the treatment roller track comprises a heat roller for the double-layer film web with a temperature level of plus / minus 0 K or from plus 1 K to plus 80 K or more in the case of high-speed double-layer film webs, especially polypropylene, in particular compared to the previous station in the machine direction and / or the roller temperature of the take-off roll.

18. blown film plant according to any one of the preceding claims, characterized in that the treatment roller track comprises a draw roll for the double-layer film web with a temperature level of minus 10 K, preferably from plus 5 K to plus 30 K, or of plus 50 K or more in the case of fast running Double layer film webs compared to the machine direction previous station.

19 blown film according to one of the preceding claims, characterized in that the one of the drafting rollers, in particular stretching rollers, a smaller roller diameter than the roller of the preceding and / or as the roller of the following station and / or as a roller of the other stations of the treatment roller track , especially with one at least 25

% or at least 50% reduced diameter.

20. blown film plant according to claim 19, characterized in that the first and the second draw roll, in particular stretching roll, both are designed with a smaller roll diameter, so that the second draw roll, the first stretch roll as a slower driven roll with a smaller roll diameter than the roll of the preceding and / or preceded by the roller of the following station and / or as a roller of the remaining stations of the treatment roller track.

21. blown film plant according to any one of the preceding claims, characterized in that the treatment roller track comprises an annealing roller for the double-layer film web with a temperature level of minus 10 K, preferably from plus 5 K to plus 30 K, or of plus 50 K or more in Trap of high-speed double-layer film webs, compared to the previous machine direction. 22. blown film plant according to any one of the preceding claims, characterized in that the treatment roller track a cooling roller for the Doppella- genfolienbahn with a temperature level of minus 10 K to minus 80 K, or minus 100 K in the case of high-speed double-layer film webs, compared with the in the machine direction previous station. 23. blown film installation according to one of the preceding claims, characterized in that the treatment roller track a threading aid with a having slidable or pivotable roller, wherein a combing depth is infinitely or stepwise adjustable.

Blown film plant according to one of the preceding claims, characterized in that a silicone insert is provided in a roll surface within the treatment roll section.

Method for producing a blown film web in a blown film line, in particular in a blown film line according to one of the preceding claims, comprising the steps a. Extruding a film tube; b. Inflating the film tube on a hose forming zone for longitudinal and transverse pulling of the film tube; c. Cooling the ascending film tube with a coolant; d. Laying the film tube to a double-layer film web using a flattening process; e. Peeling off the double-layer film web with a take-off roller pair; characterized by the further steps f. Passing the double layer film web above the take-off roller pair further up and through a treatment roller path with a heating means to heat the double-layer film web; and G. Treating the double-layer film web in the treatment roller path, in particular stretching the double-layer film web in a stretch section of the treatment roller track. Method for producing a blown film web in a blown film line, in particular in a blown film line according to one of the claims, in particular a method according to claim 25, with the steps a. Extruding a film tube; b. Inflating the film tube on a hose forming zone for longitudinal and transverse pulling of the film tube; c. Cooling the ascending film tube with a coolant; d. Laying the film tube to a double-layer film web using a flattening process; e. Peeling off the double-layer film web with a take-off roller pair; characterized by the further steps

Guiding the double-layer film web within the treatment roller path around a first draw roller and a second draw roller following one of the first draw roller, the take-off roller pair being driven at a take-off roller speed, and the second draw roller being driven at a stretch speed higher than the take-off roller speed and as the speed the first draw roll so that during operation of the blown film line (1) the double-layer film web is irreversibly stretched between the first and the second draw rolls in the machine direction, wherein a breakthrough of tensile force from the second draw roll to the take-off roll pair inhibiting punch-through brake is provided within the treatment roller path before and / or on the first draw roll, so that the punch-through brake is a bearing for receiving the tensile force.

27. The method of claim 25 or 26, wherein for threading the double-layer film web when starting the blown film system, a roller of the treatment roller path is moved or pivoted from its working position and the double-layer film web after threading by means of a return process or - is tense.

28. The method according to any one of claims 25 to 27, wherein in the treatment step g, the double-layer film web embossed, irradiated and / or subjected to a corona treatment.

29. A film produced with a blown film system according to one of claims 1 to 24 and / or by means of a method according to one of claims 25 to 28.